Other groups indicated the loss of Tfh cells in progressor, compared to nonprogressor SIV-infected RMs,36,37 and monkeys progressing faster to AIDS exhibit the loss of IL-21-secreting cells associated with involution of the GCs.111 Herein, we observed lower level of IL-21-secreting cells in MLN follicles, which is associated with a redistribution and higher expression of CXCL13, the ligand of CXCR5. The gene discussed is CXCL13; the disease is AIDS.